Given my own issues with not realizing I was pregnant, I thought it would be helpful to do a post on the timing of pregnancy testing.
Most people are familiar with the core essentials.
Unprotected sex leads to the meeting of sperm and an egg in the fallopian tube.
One hero sperm out-wriggles the others and makes its way to the warm embrace of the egg.
The fertilized egg travels to the uterus and this is where it starts to get a bit hazy.
Somehow this cluster of cells becomes a baby and a placenta, the mother’s body undergoes a huge amount of change, and all being well 9 months later a baby arrives.
But how does this happen? First, let’s get to the nitty-gritty science of it all.
What Actually Happens When You Become Pregnant?
The cluster of cells, or blastocyst, has enough energy to begin rapidly dividing as it starts to make its way down the fallopian tube towards the womb (uterus).
The uterus is prepared for its arrival by the hormone progesterone released by the ovaries earlier in the menstrual cycle.
Progesterone causes a thickened lining of blood to be laid down in your uterus.
If you do not become pregnant your levels of progesterone will fall and this uterine lining is what is shed as a period.
When the blastocyst reaches the womb it burrows into the lining of the uterus so it can start receiving nutrients from the maternal body. This is known as implantation.
Some women can feel mild cramping as the fertilized egg implants, but most will have no symptoms.
There is little scientific evidence that supports implantation bleeding, so you should not rely on it as an indicator.
Even though you are now pregnant you will still show up as negative on pregnancy tests.
What Is HCG?
Once the blastocyst has burrowed into the uterine wall it must signal to the ovaries to continue producing progesterone.
The cells that will eventually become the placenta start to produce the pregnancy hormone Human Chorionic Gonadotropin (HCG).
HCG is present in very low concentrations in the mother’s blood normally, however during the first weeks of pregnancy HCG levels rapidly increase and on average double every 48 hours.
Whether you use urine or a blood test you will be testing for the levels of HCG.
A HCG level below 5mlU/ml is normal and considered not pregnant, whereas a level above 25 mlU/ml is positive for pregnancy.
Normal (or baseline) level of HCG hormone, the amount of HCG produced in early pregnancy, and the rate at which it rises are all different for each woman making it really challenging to know when the right time to take a test is.
Add to this the uncertainty around implantation date and it’s easy to see how testing too early can give a false negative result.
How To Select Your Pregnancy Test
Home tests for pregnancy involve testing a urine sample for the levels of the hormone HCG.
The sensitivity of your pregnancy test will determine how early it is able to give you an accurate reading.
Most tests range from 20mlU/ml to 50mlU/ml.
A test with a sensitivity of 20mlU/ml can detect lower hormone levels, and so would be a better choice if you intend to take an early pregnancy test.
Follow your individual test instructions carefully, however, most tests involve adding urine to a strip and then waiting a few minutes for a control and positive line to show up.
So When Is The Earliest Time You Can Test For Pregnancy?
The earliest you could test would be 3-4 days post implantation.
As most women do not know the time of implantation a degree of guesswork is needed here.
But, as a rough guide implantation is 8-10 days post ovulation 85% of the time, whereas a period is 14 days post ovulation.
So if you know your ovulation date, 4 days before your period is due with a high sensitivity test is the earliest time you could get a positive pregnancy result.
Please be aware if you do choose to test at this time there is a high chance of a false negative if your HCG levels have not risen high enough yet.
It is recommended to perform all early pregnancy urine tests first thing in the morning as the concentration of HCG is highest in the first urination of the day.
As long as you have used sufficient levels of urine and you have a control line, even a faint positive line is a positive test.
If you do receive a faint line it is sensible to retest in a few days.
If you receive a negative test it is best to wait a couple of days before trying again.
When Is The Best Time To Test For Pregnancy
The best time to test is the first day of a missed period.
This allows plenty of time for HCG levels to have sufficiently risen and reduces the chance of negative test results.
Why Am I Showing Signs Of Early Pregnancy Already?
Levels of HCG are elevated in the blood approximately 2-3 days before this is detected in the urine.
Due to this is it possible to start feeling early signs of pregnancy even with a negative pregnancy test.
Signs to watch out for are:
- Mood swings
- Tender breasts
- Morning sickness (or food aversions)
- Food Cravings
- Feeling faint or dizzy.
Can I Get A False Positive Pregnancy Test Result?
Yes. It is rare, but no test is 100% accurate so a false positive result is possible.
Certain drugs (including fertility drugs) can cause a false positive result. You will also get a positive result with a chemical pregnancy.
What Is A Chemical Pregnancy?
A chemical pregnancy is a type of early miscarriage that occurs within the first 5 weeks of your last period.
You may have a positive test, but then begin bleeding shortly afterward.
It is believed to be caused by chromosomal abnormalities in the developing fetus and is often mistaken for a normal or late period.
Bleeding and cramping are usually similar to a menstrual period
What Is An Ectopic Pregnancy?
This is where the fertilized egg attaches to somewhere outside of the uterus (usually the fallopian tube.)
You may have early pregnancy symptoms and a positive home test but sadly the fetus cannot develop to full term outside of the uterus.
If you have watery or dark brown vaginal bleeding, tummy pain, shoulder tip pain, or discomfort going to the toilet within the first 12 weeks of pregnancy contact your healthcare provider for advice.
Can I Get A False Negative?
Yes, if the first home pregnancy test you take is before or close to implantation your HCG levels will not be sufficiently high enough and you will get a false negative pregnancy test result.